Warren Entsch was turned on.

The Coalition backbencher was then a 20-something stockman in far north Queensland and a girl at the local pub caught his eye.

"I saw this bird pass me in shorts and a boob tube," he says. "I said to the owner of the pub, 'Friggin' hell – who have you got here working for you? That's a good looking sheila. Where did she come from?'"

The stranger, it turned out, was not a stranger at all.

At the time Entsch was dating a local girl from Georgetown, 400 kilometres south-west of Cairns, and they would drink at the pub with her male cousin.

"After a few beers he would become very feminine with the other guys and would end up having a fight."

The cousin disappeared for a few months. Now Entsch discovered why: he had gone to Sydney to have a sex change operation. He returned as a woman and started work as a barmaid.

"That amazed me," Entsch says. "Imagine having the courage to do that."

It was the moment that set Entsch – dubbed a "progressive redneck" – on his path to become the Coalition's most passionate advocate for gay rights. A former crocodile hunter, grazier and RAAF serviceman, the 64-year old recognises he's the last person one would expect to find in that role.

Entsch's advocacy culminated this week when Prime Minister Tony Abbott asked him to deliver a private member's bill on same-sex marriage, co-sponsored by a Labor MP, for a vote later this year.

"The time has come," Entsch says, "to put this to the test."

Entsch's electorate, which runs from Cairns to Cape York, adjoins that of independent Bob Katter who famously said he would "walk backwards from Bourke to Brisbane" if a homosexual person could be found living in his seat.

Entsch, meanwhile, says gay people cannot be stereotyped by where they live or what they do. Two close friends – a retired pharmacist and public servant who have been in a relationship for more than 40 years – are gay.

He was thinking of such couples when he opposed John Howard's 2004 push (eventually backed by Labor) to amend the Marriage Act to explicitly state that marriage is between a man and a woman. His stance "shocked the whole party room", he says.

His long-running campaign to eliminate laws discriminating against lesbian, gay, bisexual, transgender and intersex Australians was spurred by getting to know a Special Air Service veteran who was gay. The man had depression and was worried his partner would not be able to access his superannuation if he died.

"I told that story to John Howard and it really surprised him," Entsch recalls.

"But he's SAS," Howard replied.

"I said, 'Yes Prime Minister, a person's courage is not determined by their sexual orientation.'"

He was elated in 2009 when both major parties voted to remove laws discriminating against people because of their sexuality in the treatment of tax, superannuation and social security. As he was when he co-launched a cross-party friendship group for LGBTI Australians.

"Transgender people were coming up to me in tears saying it was the first time they have felt comfortable coming into the Parliament of Australia," he says.

In recent years he has led a ginger group of Coalition politicians agitating for same-sex marriage.

"His role has been instrumental," says Greens senator Sarah Hanson-Young. "He wants to see change happen and has worked hard to bring people along with him."

Entsch had long believed the ideal time to bring on a vote would be late in the Abbott government's second full year. On Monday, following the Irish referendum legalising same-sex marriage, he told Abbott the moment had arrived.

He is "quietly confident" the Liberal party room will support a conscience vote and says a vote in Parliament will be extremely close, with a good chance of success.

Advocating for gay rights so passionately has led many people to ask him if he is gay. "I say that I don't mind what they assume I am. My sexuality is frankly irrelevant."

(His wife, he says, has been a "rock solid" supporter of his advocacy.)

As life took him in other directions, Entsch lost touch with the barmaid from Georgetown. In 2006 – after speaking publicly about their friendship – he received a letter from her thanking him.

"You are the one who has shown true courage by your acceptance, tolerance and support not only now in the national arena but also all those years ago in the smaller but potentially more hostile arena of the 'Gulf Country' of 20 years ago," she wrote.

"For the sake of those families that differ in composition to the Prime Minister's ideal I hope you are successful in your campaign."

She finished by saying she had gone back to school, finished year 12, studied medicine at university and was now working as a doctor.

The two have since reconnected and the friends share a common interest promoting LGBTI awareness among doctors in rural areas.

"I love her to pieces, I'm very proud of her," he says. "I'd like to have half as much character as she does."

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